An unclamped inductive switching (UIS) test allows investigating a dynamic avalanche failure behavior of power devices. Power devices are e.g. power MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) and IGBTs (Insulated Gate Bipolar Transistor). Power devices are frequently used in switched power supplies. Many loads driven today are inductive in nature such as solenoids, transformers, inductors and so on. A power device switching an inductive load experiences a high current flowing. So-called “rugged devices” can be designed to withstand these currents. To detect technological weaknesses of power semiconductors, for example latch-up effects or defect densities, power semiconductors may undergo an UIS test in a test facility.
During an UIS test, an electrical current flows through a power device under test (DUT) and an inductive load coupled thereto. When a predefined current level is reached, the device under test is switched off. The energy stored in the inductive load needs to be dissipated in the power device.
As an example, the device under test may be a power MOSFET. During an UIS test, the drain to source channel as a current channel of the power MOSFET transistor is forced into an avalanche breakdown after switching off due to an inductive load. A voltage snap back because of a technological weakness may destroy the power MOSFET during the avalanche breakdown. In other words, power devices are tested by an UIS test for their capability to withstand energy dissipation in the breakdown mode.
An UIS test may be effectuated on a final, i.e. packaged component. However, for example, systems comprising logical chips and power chips in one package should not undergo the UIS test after packaging because the UIS test may damage the logical chip.
For this and other reasons there is a need for the present invention.